Although many variations of printed circuit contact switches for use as keyboards and the like are known and used in the electronics industry, it has been found that a number of problems and drawbacks relating to their manufacture and use have arisen. These problems have been principally associated with their manufacturing expense, reliability of operation and to the fact that no tactile feel is transmitted to the user when the switch is actuated.
For example, U.S. Pat. No. 4,033,030 discloses a switch assembly having a circuit pattern deposited on a printed circuit board. An electrically conductive dome is provided on the upper surface of the circuit board with its periphery in electrical communication with the contactor portion of the switch printed circuit pattern. When the dome is depressed, it comes into electrical contact with the contact portion of the switch printed circuit pattern located beneath its central area, thereby completing the switch circuit.
Although this type of switch provides a positive tactile feel to the operator as the switch circuit is completed, it is relatively thick and expensive to manufacture due to its utilization of a printed circuit board. In addition, assembly problems have been experienced in locating the domes over the switch contacts and in electrical communication with the contactor portions of the circuit pattern. Furthermore, its operation has been found not to be completely reliable since the dome must electrically bridge the gap between the contact and contactor means as it is flexed, thereby presenting the possibility that complete electrical contact with the switch printed circuit pattern will not be made or maintained at either the periphery or center of the dome.
A further drawback to such switches is that they must generally be utilized with an overlying key which depresses the dome in order to insure the proper operation of the switch assembly.
In order to solve certain of the above-noted problems and drawbacks, keyboard constructions such as illustrated in U.S. Pat. No. 4,066,851 were developed which use a sheet of flexible and resilient material which supports both the contact and contactor means and which is folded upon itself in assembly to position the contact and contactor means in a spaced apart alignment.
Although such switch devices have been found to be less bulky and expensive to manufacture than the above-discussed printed circuit board switches, they have been found to be somewhat unreliable in their operation, particularly when tactile domes are utilized therewith, since the contact and contactor circuit patterns must be precisely aligned in order to insure proper electrical contact therebetween and are subject to wear. Furthermore, since the domes are formed on sheets of plastic material, their operation and tactile feel are temperature sensitive and they are subject to deterioration with use.